BEIJING(AP) Police detained four activists Wednesday after they unfurled ``Free Tibet'' banners outside the Beijing National Stadium, site of the Olympic Games' opening ceremony later this week, a pro-Tibet group said.

Three men and one woman from Students for a Free Tibet climbed two electricity poles in front of the stadium, dubbed the Bird's Nest, and unfurled the two banners at dawn, said Lhadon Tethong, the New York-based group's executive director.

One banner said ``Tibet will be free'' and the other said ``One World, One Dream'' - the slogan for the Beijing Olympics - with the words ``Free Tibet'' in Chinese. The flag of the Dalai Lama's exiled Tibetan government flew from the pocket of the one of the protesters.

After an hour, fire trucks pulled up and the protesters were peacefully led away by police and members of the internal security force, Tethong said.

``We have not had any contact with them because their phones are off,'' she said.

Her account that members of the group had been detained could not be immediately confirmed.

Sun Weide, the spokesman for the Beijing Olympics organizing committee, did not answer his telephone. Zhao Min, from the Beijing Public Security Bureau spokesman's office, said officials were trying to confirm the incident and had no immediate comment.

Tibet has been an extremely sensitive topic for Beijing since protests against almost 50 years of Chinese rule turned violent in the region's capital of Lhasa in March. Many Tibetans insist they were an independent nation before communist troops invaded in 1950, while Beijing says Tibet has been part of its territory for centuries.

Similar demonstrations were sparked in Tibetan communities throughout western China and a massive crackdown by Chinese security forces ensued.

The uprising brought a tide of critical reporting by the foreign media and turned the Olympics torch relay into a melee of protests.

``At this moment the Tibetans inside Tibet are brutally and violently being crushed by Chinese authorities,'' Tethong said. ``It's absolutely critical that ... a message is sent to the Chinese government to meaningfully address and end violence and repression in Tibet or they will never be truly accepted by the international community.''

Tethong's group identified the protesters as Iain Thom, 24, of Scotland; Lucy Marion, 23, of England; Phill Bartell, 34, of Bridgewater, New Jersey; and Tirian Mink, 32, of Portland, Oregon.